A case report of follicular lymphoma arising from the extrahepatic bile duct: interesting contrast-enhanced ultrasonographic findings.

We report a case of follicular lymphoma of the extrahepatic bile duct and the associated characteristic findings of contrast-enhanced ultrasonography (CEUS). A 60-year-old man with jaundice was scheduled to undergo surgical treatment because of a suspected diagnosis of biliary adenocarcinoma. CEUS in the high-resolution power Doppler mode showed early pulsatile enhancement of the inner layer of the thickened bile duct wall. Thereafter, gradual weak enhancement was detected in the outer layer. Extrahepatic bile duct resection was performed, and the resected specimen was diagnosed as a follicular lymphoma. On microscopic examination, the fibromuscular and deeper layers of the specimen were found to be infiltrated by follicle-forming tumor cells. The mucosal epithelium of the bile duct was almost normal. Although this is the fourth report of this condition in the English-language literature, it is the first to discuss the possibility of a preoperative diagnosis by CEUS.